In recent years, motors to be employed in home appliances have been switched from conventional ones to brushless motors in order to obtain higher efficiency from the standpoint of energy saving. This market trend has been accompanied by giving attention to a twin-rotor type three-phase brushless motor which includes magnet-rotors both inside and outside an annular stator. (disclosed in e.g. patent document 1 and patent document 2)
When the annular stator is provided with a toroidal winding, an annular stator core is generally split into equal halves. Then as shown in FIG. 12, first phase coil 60 is wound with a space remaining for a second phase coil, and then the second phase coil is wound on the space. A crossover wire is provided between the first phase coil and the second phase coil, so that it is afraid that the crossover wire sometimes touches the coils of different phases. An insulating procedure thus must be taken, such as sticking an insulating tape to both of first phase coil 60 and the crossover wire of the first phase, before the second phase coil is wound although the tape sticking is a cumbersome work. An insulating space is thus desirably prepared between the coil and the crossover wire for eliminating the tape sticking job.
The stator core provided with toroidal windings is resin-molded, in general, before it is completed as a stator of a motor. The structure of the stator core thus must withstand a high pressure of molding resin and hold an insulating space between the coil and the crossover wire. Patent document 3, for example, discloses a groove for accommodating a crossover wire in order to prevent the crossover wire from touching the coil.
Patent document 1: Unexamined Japanese Patent Application Publication No. 2005-333727
Patent document 2: Unexamined Japanese Patent Application Publication No. 2006-101656
Patent document 3: Unexamined Japanese Patent Application Publication No. H05-184092